Dryer for compressed gas

ABSTRACT

A compressed gas dryer is provided with a drying zone and a regeneration zone, and a drum rotatable in the housing containing a drying agent that is transferred successively through the drying zone and the regeneration zone, whereby said regeneration zone comprises a first subzone having a first inlet to supply a first regeneration gas flow, and a second subzone having a second inlet to supply a second regeneration gas flow of which the relative humidity is lower compared to that of the first regeneration gas flow; and that an outlet of said drying zone is connected via a connection conduit to the second inlet of the second subzone.

CROSS REFERENCE

This application is a continuation application claiming the benefit ofU.S. patent application Ser. No. 13/386,909, filed Jan. 25, 2012,granted as U.S. Pat. No. 8,608,831, which is the national stageapplication of PCT/BE2010/000053, filed Jul. 29, 2010, which claims thebenefit of Belgium application BE 2009/0484, filed Aug. 11, 2009, theentirety of said applications being incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a method for drying a compressed gasand a compressor installation provided with a dryer.

Specifically, the invention relates to a dryer provided with a rotatingdrum with therein a regenerable drying agent, which drying agent, as aconsequence of the rotation of the drum, is alternately brought throughtwo zones of the dryer, whereby in one zone, in particular, a dryingzone, said drying agent is used for drying a compressed gas, and in theother zone, more specifically, a regeneration zone, said drying agent isregenerated by bringing this drying agent into contact with a hot gas.

As a result of the rotation of the drum, regenerated drying agent willend up in the drying zone. In order to improve the performances of thedryer, it is suitable and common to provide a third zone, indicated ascooling zone, in the drum, which cooling zone allows to cool the dryingagent such that said drying agent can adsorb substantially moremoisture.

When such a dryer is used for drying a compressed gas coming from acompressor, a portion of said compressed gas is cooled to be guidedsubsequently through the drying zone of the dryer, whereby the dryingagent in this drying zone extracts moisture from said gas, whichconsequently results in a dry gas with a low pressure dew point.

The remaining fraction of the compressed gas coming from the compressorand still being hot due to the compression, is guided through theregeneration zone of the dryer, whereby said hot gas desorbs themoisture present in the drying agent, whereby the drying agent isregenerated to allow subsequently, in a new cycle, to be used again inthe drying zone to dry the compressed gas.

A disadvantage is that the compressed gas used for regeneration has arelatively high humidity, as a result of which the drying efficiency isnot optimal.

The above has the unfavourable result that, when the drying agent issubsequently brought into the drying zone, this drying agent can onlyabsorb a rather limited amount of moisture from the gas being guidedthrough said drying zone.

The heat of the compressed gas is used to regenerate the drying agent inthe regeneration zone, whereby it should be noted that, as thetemperature of the compressed gas rises, the drying process improves andthe efficiency of the installation increases accordingly.

The temperature of the compressed gas used for regeneration, can beraised by installing a heating element or the like, before guiding thisgas through the regeneration zone.

A disadvantage thereof is that the heating of the gas flow, used forregeneration, is quite expensive in view of the continuously increasingenergy prices.

The invention aims to overcome one or more of said and/or otherdisadvantages.

SUMMARY OF THE INVENTION

To that end, the invention relates to a compressor installation providedwith a compressor having an outlet, and with a dryer provided with ahousing with therein a drying zone and a regeneration zone, and a drumrotatable in the housing with therein a regenerable drying agent anddriving means for the rotation of the drum such that the drying agent ismoved successively through the drying zone and through the regenerationzone, whereby the outlet of the compressor is connected via a pressureconduit to an inlet of the drying zone; whereby said regeneration zonecomprises at least two subzones, namely, a first subzone having a firstinlet for the supply of a first regeneration gas flow, and a secondsubzone having a second inlet for the supply of a second regenerationgas flow; whereby to said pressure conduit, between the compressor andthe inlet of the drying zone, a branch is connected that connects tosaid first inlet of the first subzone; and whereby an outlet of saiddrying zone connects via a connection conduit to the second inlet of thesecond subzone, such that the relative humidity of said secondregeneration gas flow is lower than that of the first regeneration gasflow. An advantage of a compressor installation according to theinvention is that the drying agent in the second subzone comes intocontact with a gas flow of which the moisture content is considerablylower compared to the gas flow flowing through the first subzone forregenerating the drying agent in the conventional way.

Consequently, during the regeneration phase, even more moisture can beremoved from the drying agent than in the conventional way, in otherwords, in this way a further drying occurs, which can be referred to asdeep drying, causing the drying agent to adsorb more moisture from thegas to be dried in a further drying phase. A dryer according to theinvention therefore has a better performance.

According to a preferred embodiment of a compressor installationaccording to the invention, a heat exchanger is provided in saidconnection conduit.

An advantage thereof is that the second regeneration gas flow, beforebeing guided through the second subzone, can be heated by means of saidheat exchanger, as a result of which said gas flow can remove moremoisture from the drying agent.

As the temperature of the gas used for regeneration rises, the dryingprocess will improve and the efficiency of the dryer will increaseaccordingly.

Another advantage is that it is not necessary to heat the complete gasflow through the regeneration zone, but solely the second regenerationgas flow directed through the second subzone.

This brings along a number of advantages since a relatively small heatexchanger can be used, which results in an energy-saving and compactinstallation.

The invention also relates to a method for drying a compressed gascoming from an outlet of a compressor, in which method a dryer is usedprovided with a housing with therein a drying zone and a regenerationzone, and a drum rotating in the housing, with therein a regenerabledrying agent, whereby the drying agent is moved successively through thedrying zone and through the regeneration zone, and whereby thecompressed gas to be dried is guided through the drying zone while aregeneration gas is guided through the regeneration zone, whereby saidregeneration zone is divided into a first subzone through which a firstregeneration gas flow, in the form of a hot, compressed gas coming fromthe outlet of the compressor, is guided, and a second subzone throughwhich a second regeneration gas flow is guided, and whereby the secondregeneration gas flow has a lower relative humidity than the firstregeneration gas flow, and whereby the second regeneration gas flow iscomposed of a fraction of compressed gas that exits an outlet of thedrying zone.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better explain the characteristics of the present invention,a number of preferred embodiments of a dryer and compressor installationaccording to the invention, as well as a method for drying a compressedgas, are described by way of example, without being limitative in anyway, with reference to the accompanying drawings, whereby:

FIG. 1 represents schematically and in perspective view a part of adryer of a compressor installation according to the invention;

FIG. 2 represents schematically a compressor installation according tothe invention;

FIG. 3 represents schematically the layout of a part of a dryer of acompressor installation according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a part 1 of a dryer of a compressor installation accordingto the invention, for compressed gas. The part 1 of the dryer isprovided with a housing 2 with therein a drying zone 3, a cooling zone 4and a regeneration zone 5 which, according to the specificcharacteristic of the invention, comprises two subzones, a first subzone6 and a second subzone 7 respectively.

Preferably, said first subzone 6 connects to the end of drying zone 3,while the second subzone 7 connects to the first subzone 6 and isfollowed by the cooling zone 4 which in its turn connects to thebeginning of the drying zone 3.

Therefore, the first subzone 6 is situated at the beginning of theregeneration zone 5, or in other words, at the part of the drying zone 3via which, during operation of the dryer, the moist drying agent 8enters the regeneration zone, while the second subzone 7 is situated atthe end of the regeneration zone 5, or, in other words, at the part ofthe regeneration zone via which the regenerated drying agent 8 exits theregeneration zone 5 and enters the cooling zone 4.

By “the end of the drying zone 3” is meant, the part of the drying zone3 via which the humid drying agent 8 exits the drying zone 3 duringrotation of the drum 9, whereas by “the beginning of the drying zone 3”is meant, the part of the drying zone 3 in which fresh regenerateddrying agent 8 enters.

A rotating drum 9 is mounted in the housing 2 in which drum 9 isprovided a drying agent 8, or so-called desiccant.

The dryer 1 is also provided with driving means, not represented in thefigures, for example in the shape of a motor, for enabling the rotationof the drum 9 such that the drying agent 8 is moved successively throughthe drying zone 3, the regeneration zone 5 and the cooling zone 4.

FIG. 2 shows a compressor installation according to the invention whichcomprises, besides said part 1, a pressure conduit 10 making aconnection between the outlet of a compressor 11 and an inlet of thedrying zone 3. The compressor 11 also forms part of the compressorinstallation.

To said pressure conduit 10, between the outlet of the compressor 11 andthe inlet of the drying zone 3, a branch 12 connects, which is connectedto a first inlet of said first subzone 6.

Furthermore, a return conduit 13 is provided for the gas flows, used forregeneration and cooling, which return conduit 13 connects the commonoutlet, of the first and second subzones 6 and 7 of the regenerationzone 5 and of the cooling zone 4, to the pressure conduit 10 and ends uptherein nearby a venturi 14 provided in the pressure conduit 10. Acooler 15 is provided in this return conduit 13.

At the outlet of the drying zone 3 is provided, on the one hand, atake-off point 16 along which the dried gas can be discharged forfurther use and, on the other hand, with a connection conduit 17 whichguides a fraction of the dried gas through the secondary side of a heatexchanger 18, and subsequently guides this fraction through the secondsubzone 7 of the regeneration zone 5.

In the pressure conduit 10 an aftercooler 19 is provided between thecompressor 11 and the venturi 14.

The method according to the invention for drying a compressed gas, isvery simple, and as follows.

The flow directions are indicated in the figures. Arrow A shows the flowdirection of the main flow through the drying zone 3 of the dryer. Theflow direction of the remaining gas flows through the regeneration- andcooling zone, is, in the example as shown, directed opposite withrespect to the flow direction A of the main flow, as illustrated byarrows B, D and E. Arrow C indicates the sense of rotation of the drum 9in the housing 2 of the dryer.

The gas to be dried, coming from the compressor 11 or at least asubstantial portion thereof, flows, in the form of a main flow, afterpassage through the aftercooler 19, through the drying agent 8 in thedrying zone 3 towards the outlet of the drying zone 3, whereby, bymaking contact with the drying agent 8, the moisture is adsorbed by saiddrying agent 8. The gas dried in that way, is discharged via a take-offpoint 16 towards a consumers network situated downstream.

The drum 9 transfers the moisture-laden drying agent 8 to the firstsubzone 6 of the regeneration zone 5, where the moisture in the dryingagent 8 is desorbed by contacting this drying agent 8 with a firstregeneration gas flow in the form of a hot, compressed gas that, viabranch 12, is supplied from the outlet of the compressor 11, toaccomplish as such a first regeneration of the drying agent 8, makinguse of the heat of compression present in said first regeneration flow.

According to the specific characteristic of the invention, at the endingof the movement of the drying agent 8 through the regeneration zone,this drying agent is dried further in the second subzone 7 of theregeneration zone 5, than was possible until now, by bringing the dryingagent 8 into contact with a second regeneration gas flow of which therelative humidity is lower than that of the first regeneration gas flow.

To this aim, the second regeneration gas flow in this case consists ofgas that is branched off from the dried gas that exits the drying zone 3and that, before being supplied to the regeneration zone 5 via the inletof the second subzone 7, is guided through the secondary side of theheat exchanger 18, in which said gas flow is heated, in order to lowerthe partial pressure of the water present in this gas.

It is clear that in this way the moisture content of the drying agent 8during regeneration can be reduced considerably due to the fact that thedrying agent 8 is after-dried in the second subzone 7 of theregeneration zone 5 by making use of a hot, dry gas having low relativehumidity. This is the most important advantage of the dryer and methodaccording to the invention.

As the drum 9 rotates further, more moisture is being withdrawn from thedrying agent 8, until the drying agent 8 reaches the drying zone 3,after first being cooled in the cooling zone, disposed of the adsorbedmoisture, such that the drying agent 8 regenerated as such can be usedduring a subsequent cycle of drying in the drying zone 3.

As such, the drying agent 8 is guided alternately through the dryingzone 3 and subsequently through the regeneration zone 5, in a continuousor discontinuous movement of revolution.

According to the invention, it is appropriate that a fraction of thedried main gas flow is used for cooling the hot regenerated drying agent8 at the transition between the regeneration zone 5 and the drying zone3 in the cooling zone 4, before said drying agent 8 comes into contactwith the main flow in the drying zone 3.

The presence of such a cooling zone 4 is after all advantageous in thatthe main flow is not coming into contact with hot drying agent 8 that isnot able to adsorb liquid and that would cause the humid gas to leakthrough the dryer 1. Consequently, in this manner the drying isoptimised.

Thanks to the venturi 14 a local pressure drop is generated in a knownway, which results in that the outlet of the regeneration zone 5 remainsunder a lower pressure than at the outlet of the drying zone 3 situatedat the opposite side of the drum 9, as a result of which a fraction ofthe cool main gas flow from the outlet of the drying zone 3 flowstowards the outlet of the regeneration zone 5, through the cooling zone4 situated between drying zone 3 and regeneration zone 5.

By guiding this flow through the cooling zone 4, the hot regenerateddrying agent 8 will be cooled with advantageous effect, before saiddrying agent 8 is used to dry the main gas flow.

The lower pressure described above further causes the gas coming fromthe drying zone 3, to flow through the heat exchanger 18, towards thesecond subzone 7. Said flow is in particular made possible by taking offdry gas at the correct position, namely at a position where the dynamicpressure is the lowest. Thus, no blowers are required for this system.

The gas used for regeneration and cooling of the drying agent 8 is,after flowing through the respective zones, collected and cooled bymeans of a cooler 15, after which this gas is added to the main gasflow, that, subsequently, in its turn, is guided through the drying zone3.

FIG. 3 shows an example of a schematic lay-out of a part 1 of a dryeraccording to the invention, whereby the different sectors or zones aremade visible.

This figure shows in particular how the regeneration zone 5 is dividedinto two subzones 6 and 7, whereby in this case the regeneration zone 5extends over a circumferential angle of almost 90 degrees.

In this case, the first subzone 6 extends over an angle of 75 degrees,while in this example the second subzone 7 extends over an angle in arange from 5 degrees to 30 degrees, and in this case over an angle ofalmost 15 degrees.

In this example, the drying zone 3 comprises a circle sector of 255degrees, while the remaining part of 15 degrees, between the secondsubzone 7 and the drying zone 3, forms the cooling zone 4 in thecylindrical housing 2 of the dryer.

It is clear from the figure in which sense the different zones in thedrum 9 are preferably being passed through.

It is clear that the second regeneration gas flow can be heated as wellby guiding said flow through a heating element or the like, notrepresented in the figures.

The gas which is guided through the second subzone 7 should notnecessarily come from the dryer itself, however, it can originate froman external source of dried gas as well.

The present invention is by no means limited to the embodimentsdescribed by way of example and represented in the drawings, however acompressor installation according to the invention and a method fordrying a compressed gas can be realized in many ways, without departingfrom the scope of invention.

The invention claimed is:
 1. A dryer for compressed gas comprising ahousing having a drying zone and a regeneration zone therein, and a drumwhich is configured to rotate in the housing, and comprises aregenerable drying agent therein and a driver for rotation of the drumconfigured such that the drying agent is moved successively through thedrying zone and through the regeneration zone wherein said regenerationzone comprises at least two subzones, namely, a first subzone having afirst inlet for a supply of a first regeneration gas flow, and a secondsubzone having a second inlet for a supply of a second regeneration gasflow, wherein a relative humidity of the second regeneration gas flow islower than a relative humidity of the first regeneration gas flow, andwherein an outlet of said drying zone connects to the second inlet ofthe second subzone via a connection conduit, and wherein said secondsubzone is situated at the end of the regeneration zone.
 2. The dryeraccording to claim 1, wherein the regeneration zone extends over a firstcircumferential angle of almost 90 degrees and the second subzoneextends over a second circumferential angle ranging between 5 degreesand 30 degrees.
 3. The dryer according to claim 1, wherein a heatexchanger is provided in said connection conduit.
 4. The dryer accordingto claim 1, wherein the first subzone and the second subzone have acommon outlet.
 5. The dryer according to claim 4, wherein said commonoutlet of the first subzone and of the second subzone connects through areturn conduit to a pressure conduit, which is configured to supply thecompressed gas to be dried, via an aftercooler, to an inlet of thedrying zone.
 6. The dryer according to claim 1, wherein a temperature ofthe second regeneration gas flow at the second inlet of the secondsubzone is larger than or equal to a temperature of the firstregeneration gas flow at the first inlet of the first subzone.
 7. Thedryer according to claim 2, wherein a heat exchanger is provided in saidconnection conduit.
 8. The dryer according to claim 2, wherein the firstsubzone and the second subzone have a common outlet.
 9. The dryeraccording to claim 3, wherein the first subzone and the second subzonehave a common outlet.
 10. The dryer according to claim 7, wherein thefirst subzone and the second subzone have a common outlet.
 11. The dryeraccording to claim 8, wherein said common outlet of the first subzoneand of the second subzone connects through a return conduit to apressure conduit, which is configured to supply the compressed gas to bedried, via an aftercooler, to an inlet of the drying zone.
 12. The dryeraccording to claim 9, wherein said common outlet of the first subzoneand of the second subzone connects through a return conduit to apressure conduit, which is configured to supply the compressed gas to bedried, via an aftercooler, to an inlet of the drying zone.
 13. The dryeraccording to claim 10, wherein said common outlet of the first subzoneand of the second subzone connects through a return conduit to apressure conduit, which is configured to supply the compressed gas to bedried, via an aftercooler, to an inlet of the drying zone.
 14. The dryeraccording to claim 2, wherein a temperature of the second regenerationgas flow at the second inlet of the second subzone is larger than orequal to a temperature of the first regeneration gas flow at the firstinlet of the first subzone.
 15. The dryer according to claim 3, whereina temperature of the second regeneration gas flow at the second inlet ofthe second subzone is larger than or equal to a temperature of the firstregeneration gas flow at the first inlet of the first subzone.
 16. Thedryer according to claim 4, wherein a temperature of the secondregeneration gas flow at the second inlet of the second subzone islarger than or equal to a temperature of the first regeneration gas flowat the first inlet of the first subzone.
 17. The dryer according toclaim 5, wherein a temperature of the second regeneration gas flow atthe second inlet of the second subzone is larger than or equal to atemperature of the first regeneration gas flow at the first inlet of thefirst subzone.
 18. The dryer according to claim 11, wherein atemperature of the second regeneration gas flow at the second inlet ofthe second subzone is larger than or equal to a temperature of the firstregeneration gas flow at the first inlet of the first subzone.
 19. Thedryer according to claim 12, wherein a temperature of the secondregeneration gas flow at the second inlet of the second subzone islarger than or equal to a temperature of the first regeneration gas flowat the first inlet of the first subzone.
 20. The dryer according toclaim 13, wherein a temperature of the second regeneration gas flow atthe second inlet of the second subzone is larger than or equal to atemperature of the first regeneration gas flow at the first inlet of thefirst subzone, and wherein said driver is a motor.